Diabetes Prevalence in the US May Have Plateaued

Miriam E Tucker

September 08, 2015

Approximately 12% to 14% of American adults had diabetes in 2011–2012, roughly the same as in 2007–2008, new national estimates show.

The findings, extrapolated from the National Health and Nutrition Examination Survey (NHANES), were reported in the September 8 issue of the Journal of the American Medical Association by Andy Menke, PhD, of Social & Scientific Systems, Silver Spring, Maryland, and colleagues from the US Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH).

Based on 2781 participants in 2011–2012 and using any method for defining diabetes (HbA1c, fasting plasma glucose, or 2-hour oral glucose tolerance test),the authors calculate that 14.3% of the total population over age 20 years had diabetes, 9.1% had diagnosed diabetes, 5.2% undiagnosed diabetes, and 38.0% had prediabetes.

Among those with diabetes, more than a third — 36.4% — were undiagnosed overall. That's significantly less than in 1988–1994 — the age-standardized proportion dropped from 40.3% to 31.0% (P < .001).

But the proportion of undiagnosed diabetes remains higher among Asian and Hispanic individuals, at 50.9% and 49%, respectively, Dr Menke and colleagues note.

"Certainly the most encouraging trend was the decrease during 1988–2012 in the proportion of diabetes that was undiagnosed. This was found in all groups, except in the very youngest that we studied — age 20 to 44 years — and in Mexican Americans," principal investigator Catherine C Cowie, PhD, director of the diabetes epidemiology program at the National Institute of Diabetes and Digestive and Kidney Diseases, told Medscape Medical News.

However, she said, "The high prevalence of prediabetes, together with the high prevalence of undetected diabetes, especially in Asian and Hispanic groups, highlights the need for improved screening by the medical community that is targeted to high-risk groups. Individuals with undiagnosed diabetes need treatment to avoid or delay the complications of diabetes."

A Glimmer of Hope? Prevalence Levels Plateau…

Diabetes prevalence (using just HbA1c or fasting plasma glucose) increased from 9.8% in 1988–1994 to 12.7% in 2007–2008 but then hadn't risen further by 2011–2012 (12.4%).

These data parallel the leveling off of obesity and offer a "glimmer of hope," say William H. Herman, MD, MPH, and Amy E Rothberg, MD, PhD, both of the University of Michigan, Ann Arbor, in an accompanying editorial.

"These findings suggest that the recommendations issued by the US Surgeon General and the Institute of Medicine; the implementation of food, nutrition, agricultural, and physical-activity policies; regulations by federal, state, and local governments; and the focus on individual behavioral change related to diet and physical activity by the US CDC have begun to affect the prevalence of obesity and, secondarily, after a delay of approximately 10 years, the prevalence of type 2 diabetes," Drs Herman and Rothberg write.

Dr Cowie told Medscape Medical News, "We share Dr Herman's hope that the plateauing of prevalence during the latter years of the observation period of our analysis will continue."

However, "as this is based only on three time points, caution is needed in concluding that this prevalence is stable," she stressed.

Diabetes Prevalence, Undiagnosed Diabetes Higher in Minorities

Diabetes was diagnosed by an HbA1c of 6.5% or greater, a fasting plasma glucose level of 126 mg/dL or greater, or a 2-hour plasma glucose level of 200 mg/dL or greater. For prediabetes, those cutoffs were 5.7% to 6.4%, 100 to 125 mg/dL, and 140 to 199 mg/dL, respectively.

Using all three methods, the age-standardized prevalence of diabetes was 11.3% among white, 21.8% among black, 20.6% among Asian, and 22.6% among Hispanic participants.

Age-adjusted mean body mass indexes (BMIs) were 28.4, 30.8, 24.6, and 29.7 kg/m2, respectively, among the respective racial groups, and all these values were statistically different between the white and other groups.

The lower BMI in Asians might explain the high rate of undiagnosed diabetes in this group.

"The high proportion of diabetes that was undiagnosed in this population may not be surprising, given the relatively low average BMI in this group, which would be less likely to spur testing for type 2 diabetes by medical professionals," Dr Cowie observed.

Indeed, because Asian individuals may have a higher percentage of body fat and higher risk of developing diabetes at a given BMI, the World Health Organization has suggested lower BMI cut points for defining overweight and obesity in Asian individuals, the authors note.

Curbing the Obesity (and Diabetes) Epidemic

In their editorial, Drs Herman and Rothberg credit the "shift in cultural attitudes toward obesity, the American Medical Association's recognition of obesity as a disease, and the increasing focus on societal interventions to address food policy and the built environment" as forces contributing to curbing the obesity (and type 2 diabetes) epidemic.

They add, "Providing insurance coverage for intensive behavioral therapies for obesity and using behavioral economic approaches to encourage their uptake are further removing barriers to patient engagement and are providing strong incentives for individual behavioral change.…Progress has been made, but expanded and sustained efforts will be required."

Dr. Cowie told Medscape Medical News that the National Diabetes Education Program — a partnership between NIHealth and the CDC — has many resources to help clinicians care for their patients at risk for or diagnosed with diabetes.

The program also has many materials — several in multiple languages — for people with or at risk for diabetes to learn about risk factors for diabetes, how the condition is diagnosed, how to manage diabetes for those who have it, and many other topics.

Dr Cowie, Dr Menke, and coauthors have no relevant financial relationships. Dr Herman reported receiving personal fees and other from Merck Sharp & Dohme and Lexicon Pharmaceuticals and personal fees from Profil Institute for Clinical Research. Dr Rothberg reported no relevant financial relationships.

JAMA. 2015;314:1021-1029, 1005-1007. Abstract, Editorial


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